The base of the following pyramid is a square. If the
surface area of the pyramid is 400 feet^{2}, what is the missing
length? Round the answer to the nearest hundredth.

The missing length is feet.

SA = Base Area + 4 × Area of a triangle

Area of a triangle = 1/4 × (400 - 14 × 14)

= 51 feet^{2}

l = (2 × 51) ÷ 14

= 7.29 feet

The missing length is 7.29 feet.